1. Field of the Invention
The present invention relates to a burner for premixing liquid and gaseous fuels during a graduated load operation in a combustion chamber.
2. Background of the Invention
EP-B1-0 321 809 discloses a conical burner that consists of several shells stacked inside each other and that is used to create a closed rotational flow in the cone head. Because of the increasing rotation along the cone tip, this rotational flow becomes unstable and then changes to an annular rotational flow with a backflow bubble in the core. With this burner, gaseous fuels are preferably injected in the flow direction along air inlet channels and are mixed homogeneously with the air flowing in, before the combustion starts as a result of the ignition at the backup point of the backflow bubble. The air inlet channels are formed by the shells which extend, offset to each other, in the longitudinal direction of the burner. The backflow bubble performs the function of a bodiless flame holder. Liquid fuels are injected preferably via a central nozzle at the burner head, and they then evaporate in the conical cavity formed by the shells. During the operation of such a burner, which indisputably is characterized by minimal noxious emissions, it was found that for operation with a gaseous fuel, a longer premixing section would actually be advantageous, while for an operation with a liquid fuel the long premixing section results in compromises regarding the injection of the liquid fuel.